A woman was shot and killed on Tuesday night just steps from the popular tourist areas of Union Square and the Westfield Mall, bringing San Francisco's homicide count for 2015 to 39.

San Francisco Police Department spokesperson Officer Grace Gatpandan says that at 8:08 Tuesday night, police were called to the 100 block of Mason Street, which is between Eddy and Ellis Streets, on reports of a shooting.

When officers arrived, the discovered a woman who had been shot in the upper torso. Though officers performed CPR, she died at the scene.

As of publication time, the San Francisco Medical Examiner's office had not publicly identified the victim, and Gatpandan did not have any additional details on the woman to report.

However, Gatpandan does confirm that a "person of interest" was identified and transported to Tenderloin Station for further questioning. As of Wednesday morning, that person is still being questioned by homicide investigators, Gatpandan says, but has yet to be arrested.

Eagle-eyed readers will note that when we last checked with SFPD on on San Francisco's homicide count (yesterday!), the number stood at 36 confirmed, with a possible 37th pending confirmation. So how did we get to 39? By phone this morning, Gatpandan reminded us that SFPD's list is in constant flux, as investigation and Medical Examiner decisions can turn deaths "that were [considered] homicides into suicides, or people can die long after" they were mortally wounded as happened earlier this year.

"The number is not written in stone," Gatpandan said, and the best thing we can do is to keep checking in with SFPD's count and to follow-up on cases that have changed status.

Anyway, back to the case at hand. As Gatpandan says the last night's slaying remains under investigation, and the SFPD is eager to speak with anyone with information on the crime. If you know something about this shooting, please contact the SFPD Anonymous Tip Line at 415-575-4444 or to text a tip to TIP411 with SFPD at the beginning of the message.